Rice is a food that is consumed in the entire earth and within its processing, it is necessary to remove the husk. Particularly, for each ton of uncollected rice a quarter of a ton of rice husks is produced, which is mostly treated as agricultural residue.
For example, in Mexico 337,250 tons of rice are produced yearly, which represents 84,312 tons of rice husks per year.
Due to the worldwide high production of rice, it is important to find applications of residue (husk), produced during its processing. Its high content of silica, its uniform thickness geometry and aspect relation, make it a material that is economically viable to work as load (filling material) in resin binder, similar to wood particles used in the manufacture of conglomerates. Within the manufacturing process of wood binders, the resin proportion used orders the mechanical resistance of the end product. That is, the greater the resin concentration, the greater the mechanical resistance and resultant production cost. From the nanostructure point of view, carbon nanotubes, besides other properties, are highly resistant and can cause significant increase on the mechanical properties of a material, if employed as support nanoload.
On the other hand, it is also known that the housing market is an important economic engine in any country, and Mexico is not an exception. The composition of a building destined for housing is very complex: it requires a great number of materials and labor from an assortment of specialties, as well as from the construction process chosen therefor. However, all these constructions have similar features regarding shape and behavior. All of them are composed of walls, and at least one horizontal component defined by systems of floors and ceilings.
We have noticed that wood and its conglomerates can be used within a full constructive system, from basic structure to finishing work. Notwithstanding, the ecological part and the cost from the distinct processes for treating the same can be very high, and negatively affect a generation of inexpensive or affordable housing, even when panels made of process residues and synthetic resin binding particles are generated.
Within this problem, we propose manufacturing cheaper products with better performance by combining four elements, namely agroindustrial residue materials, polymeric resins, cements and carbon nanostructures. On one hand, it has been shown that it is possible to mix resins with carbon nanotubes in order to achieve a better mechanical and driving performance. Furthermore, the rice husk (with or without thermal treatment) can become an inexpensive material because it is a waste, and thus it can be used to manufacture more inexpensive composite materials (conglomerates, pastes and paints) employing a carbon nanotube modified resin and a cement material (white cement and Portland gray cement are examples). These new compounds are conceived as construction materials, which are parts of the construction system due to their mechanical properties as well as materials for finishes allowing building of low cost housing.
The material of the present disclosure has advanced nanotechnology engineering, in addition to having as a base element an agricultural field residue produced in every region of the world, and its application as fodder is not possible. Thus, our solution is considered as having significant ecological contributions.
Silica oxide is present in the husk, and this is part of the composed or composite material for construction. Same does not represent any health risk since the silica is confined in the rice husk structure and the latter one is in turn inside the material polymeric matrix, eliminating the risk of detachment from said particles that may cause harm to people who may come into contact with the same.
By offering fireproof properties, the material of the present disclosure is considered an appropriate finish for places of massive concentration of people as fire-retardant, and this gives added value to housing where it is applied.
Since its constituents give it the property of not transmitting heat surrounding its side exposed to the outside (for having a micro scale porous structure and high silica content) it also passively participates in saving energy, including electric energy, to achieve comfort inside the building to which it is applied. We have found that the performance of a 3 mm thick paste is significantly superior than the performance of 2 inch thick polystyrene sheeting.
Likewise, the composed or composite material of the disclosure is made up of ecological materials and has the ability of being a wood substitute material for building houses and other buildings. Its contribution to the environment reaches an elevated impact since it stops using materials that indirectly generate high volumes of CO2 during their manufacture.
In addition, we propose the mixing and pressing procedure of a cementing material with rice husk with or without thermal treatment, bound with carbon nanostructure modified polymeric resin as support load. The procedure allows that when varying the proportions between these materials, a conglomerate, paste or paint may be produced in order to incorporate it as a substitute and novel material in the existing construction systems.
Briefly, the rice husk material of the present disclosure can be used in the preparation of: paints, with fireproof properties, great mechanical resistance, and thermal and impermeable insulation properties; and pastes, to directly apply on walls as texturized finish, withy thermal isolating properties with thickness of 2 mm or more, fireproof properties and with mechanical resistance to stress and impermeable.
The present rick husk based material can also be used in the preparation of panels in different thicknesses and densities, with high bending, tension and compression mechanical properties, fireproof and thermal isolating properties, in addition to being resistant to constant hydrostatic pressures (with no thickness increase) for a long time and for its silica content also resistant to termites, while also presenting thermo-modeling properties.